Dynamical structure of aqueous solutions of biological substance by microwave dielectric relaxation

1. 采用TDR和波导干涉法测定了0.1（小于等于）v/GHz（小于等于）89频率范围内乙醇/水和乙二醇/水混合物的复介电光谱。在0.3（小于或等于）X（醇的摩尔分数）<或等于)1.0处，除了占主导地位的低频过程（j=1）被分配给氢键系统的协同动力学外，还需要另外两个松弛时间为τ_2 ~ 10-20ps和τ_3 ~ 1-2ps的Debye项（j=2和j=3）来重现光谱的高频部分。这可以分别归因于链末端的单h键醇单体的运动和自由OH的翻转运动。当X<0.3时，j=2进程不再可分离。多余的活化自由能ΔG^E、焓ΔH^E和熵ΔS^E，以及它们的偏摩尔量ΔG^E_i、ΔH^E_i和ΔS^E_i （i=醇和水）由协同反应过程的弛豫时间τ_1导出。当X【大于或等于】X_b时（如X_b ~ 0.15，对于2-丙醇/水），ΔH^E_A和ΔS^E_A趋近于零，表明生成了类似纯醇的之字形h键醇链。ΔH^E_A和ΔS^E_A的两个相关最大值（例如，2-丙醇/水在X ~ 0.03和~ 0.07处）被解释为氢键数量和强度同时增加，并支持这样的观点，即在中间区域，由于溶质-溶质结合，水分子从非极性基团的第一配位壳中被推出到体中，称为疏水相互作用。2-丙醇/水和1-丙醇/水的结果比较表明，非极性头基的大小和对醇OH的位阻是控制氢键体系协同动力学的关键因素。我们彻底地研究了氨基酸的水溶液；使用DRS在25℃下，频率范围0.1（小于等于）v/GHz，频率范围小于等于0.1 v/GHz，频率范围0.1 v/GHz，频率范围0.1 v/GHz。三个松弛过程；两性离子氨基酸分子的旋转扩散（τ_1 ~ 40 ~ 110ps）、体积水分子的协同动力学（τ_2 ~ 8 ~ 11ps）和单氢键水分子的快速旋转（τ_3 ~ 1 ~ 2ps）。将卡维尔方程分别应用于溶质过程和溶剂过程，推导出了每种氨基酸的偶极矩和有效水化数Z，即每个溶质中不能参与溶剂弛豫过程的水分子数。利用Stokes-Einstein-Debye （SED）方程将氨基酸分子作为旋转物质的有效摩尔体积与它们的偏摩尔体积进行比较，结果表明，在流体动力学滑移边界条件下，氨基酸的形状因子f_⊥（表示偏离球形）随着侧链基团的大小线性增加，但l -脯氨酸具有刚性环状结构的情况除外。少

1. We determined the complex dielectric spectra of alcohol/water and ethylene glycol/water mixtures in the frequency range of 0.1【less than or equal】v/GHz【less than or equal】89 using TDR and wave guide interferometry. At 0.3【less than or equal】X (molar fraction of alcohol)【less than or equal】1.0, besides the dominating low-frequency process (j=1), assigned to the cooperative dynamics of the H-bond system, two additional Debye terms (j=2 and j=3) with the relaxation times of τ_2〜10-20ps and τ_3〜1-2ps are required to reproduce the high-frequency part of the spectrum. These can respectively be assigned to the motion of singly H-bonded alcohol monomers at the ends of the chain structure and the flipping motion of free OH. At X<0.3, the j=2 process becomes no longer separable.2. The excess activation free energy, ΔG^E, enthalpy, ΔH^E, and entropy, ΔS^E, and their partial molar quantities, ΔG^E_i, ΔH^E_i, and ΔS^E_i (i=alcohol and water) were derived from the relaxation time of the cooperati … More ve process, τ_1. In X【greater than or equal】X_b (ex. X_b〜0.15, for 2-propanol/water), ΔH^E_A and ΔS^E_A become nearly zero, suggesting the generation of zigzag H-bonded alcohol chains similar to the pure alcohol. The two pertinent maxima in ΔH^E_A and ΔS^E_A (ex. at X〜0.03 and 〜0.07 for 2-propanol/water) are interpreted as a simultaneous increase of the number and strength of H-bond and support the view that in the intermediate region, water molecules are pushed out of the first coordination shell of the non-polar group into the bulk due to solute-solute association, called hydrophobic interaction. The comparison of the result of 2-propanol/water to that of 1-propanol/water revealed that not only the size of non-polar head group but the steric hindrance to alcohol OH are the key factor that controls the cooperative dynamics of H-bond system.3. We thoroughly investigated aqueous solutions of amino acids; glycine, L-alanine, L-valine, L-leucine, L-isoleucine, L-serine, L-thoreonine, L-proline, L-cysteine, L-methionine, and L-Phenylalanine using DRS at 25℃ in the frequency range 0.1【less than or equal】v/GHz【less than or equal】89. The three relaxation processes; the rotational diffusion of zwitterionic amino acid molecules (τ_1〜40-110ps), the cooperative dynamics of bulk water (τ_2〜8-11ps), and a fast rotation of singly H-bonded water molecules (τ_3〜1-2ps) were detected. Applying the Cavell equation respectively to the solute and solvent processes, the dipole moment of each amino acid and the effective hydration number, Z, corresponding to the number of water molecules per solute that cannot contribute to the solvent relaxation processes, were deduced. A comparison of the effective molar volume of amino acid molecules as a rotational species estimated from τ_1 using the Stokes-Einstein-Debye (SED) equation to their partial molar volume, revealed that the shape factor of the amino acids under the hydrodynamic slip boundary condition, f_⊥, representing deviation from a spherical shape, increases linearly with the size of the side chain group except the case of L-proline that possesses a rigid ring-like structure. Less